You don't want derogatory national stereotypes, but the whole notion of a stereotype is derogatory. Check your dictionary. The word "oversimplified" is part of the definition of the word "stereotype." All stereotypes have a negative connotation because they're applied to people or things for which they are clearly false.
Avoid stereotyping the people of a nation. The practice is pejorative in nature.
@krass You're not an insightful reader. All national stereotypes are derogatory [i]per se[/i], and that's why we all should refrain from using or repeating them. Simple enough now, or still too complicated for your reading level?